Discharge lamp for GDS with an axial magnetic field

Abstract

A glow discharge spectrometer discharge lamp includes: a lamp body having a vacuum enclosure connected to pump elements and to injector elements for injecting an inert gas into the enclosure; a hollow cylindrical first electrode of longitudinal axis X-X′; a second electrode for receiving a sample for analysis and for holding the sample facing one end of the cylindrical electrode; electric field generator including an applicator for applying to the terminals of the electrodes an electric field that is continuous, pulsed, radiofrequency, or hybrid, and suitable for generating a glow discharge plasma in the presence of the gas; coupler elements for coupling the discharge lamp to a spectrometer suitable for measuring at least one component of the plasma; and magnetic field generator elements for generating a magnetic field having field lines oriented along the axis X-X′, the magnetic field being uniform in orientation and in intensity over an area of the sample that is not less than the inside area of the hollow cylindrical electrode as projected along the direction X-X′.

The invention claimed is: 
     
       1. A glow discharge spectrometer discharge lamp ( 1 ) comprising:
 a lamp body having a vacuum enclosure ( 6 ) connected firstly to pump means ( 8 ) and secondly to injector means ( 10 ) for injecting an inert gas into said enclosure ( 6 ); 
 a hollow cylindrical first electrode ( 2 ) of longitudinal axis X-X′; 
 a second electrode ( 4 ) suitable for receiving a sample ( 12 ) for analysis and for holding the sample ( 12 ) facing one end of the cylindrical electrode ( 2 ); 
 electric field generator means comprising an applicator ( 3 ) for applying to the terminals of said electrodes ( 2  and  4 ) an electric field that is continuous, pulsed, radiofrequency (RF), or hybrid, and that is suitable for generating a glow discharge plasma ( 11 ) in the presence of the gas ( 10 ); 
 coupler means ( 16 ) for coupling the discharge lamp to a spectrometer that is suitable for measuring at least one component of said plasma ( 11 ); and 
 magnetic field generator means for generating a magnetic field; 
 the lamp being characterized in that: 
 the magnetic field generator means are suitable for generating a magnetic field having field lines that are oriented along the axis X-X′, said magnetic field being uniform in orientation and in intensity over an area of the sample ( 12 ) that is not less than the inside area of the hollow cylindrical electrode ( 2 ) as projected along the direction X-X′. 
 
     
     
       2. A discharge lamp according to  claim 1 , characterized in that the magnetic field generator means comprise at least one magnet ( 13 ) arranged behind the electrode ( 4 ), with the axis joining its poles being parallel to the axis X-X′ and with its dimensions in directions transverse to the axis X-X′ being greater than the projected inside area of the electrode ( 2 ). 
     
     
       3. A discharge lamp according to  claim 2 , characterized in that the magnetic field generator lines comprise a magnet ( 13 ) in the form of a solid cylinder of axis X-X′ and arranged behind the electrode ( 4 ). 
     
     
       4. A discharge lamp according to  claim 2 , characterized in that the magnetic field generator means comprise at least one magnet ( 13 ) of annular shape arranged around the hollow cylindrical electrode ( 2 ) and for which the axis joining its poles is parallel to the axis X-X′ of said electrode ( 2 ). 
     
     
       5. A discharge lamp according to  claim 2 , characterized in that the magnetic field generator means comprise one or more NbFeB magnets. 
     
     
       6. A discharge lamp according to  claim 2 , characterized in that the magnetic generator means comprise one or more magnets ( 13 ) arranged in a metal coupler ( 15 ) and held in said coupler ( 15 ) by electrically insulating parts, said coupler ( 15 ) being connected firstly to the second electrode ( 4 ) and secondly to the electric field applicator ( 3 ) in such a manner that the magnetic axis of said magnet(s) ( 13 ) coincide(s) with the axis X-X′. 
     
     
       7. A discharge lamp according to  claim 2 , characterized in that the magnetic field generator means comprise an electromagnetic coil of axis parallel to the axis X-X′. 
     
     
       8. A discharge lamp according to  claim 2 , characterized in that it includes cooling means suitable for cooling the magnetic field generator means. 
     
     
       9. A discharge lamp according to  claim 2 , characterized in that the magnetic field generator means present dimensions extending transversely relative to the axis X-X′ that are greater than the projected inside area of the hollow cylindrical electrode ( 2 ) so as to generate a magnetic field that is uniform in intensity and in orientation over the area of the sample ( 12 ) facing the end of said electrode ( 2 ). 
     
     
       10. A discharge lamp according to  claim 2 , characterized in that it includes means for measuring the intensity of the magnetic field and suitable for comparing the intensity of the magnetic field at the sample ( 12 ) with a predetermined threshold. 
     
     
       11. A discharge lamp according to  claim 1 , characterized in that the magnetic field generator lines comprise a magnet ( 13 ) in the form of a solid cylinder of axis X-X′ and arranged behind the electrode ( 4 ). 
     
     
       12. A discharge lamp according to  claim 1 , characterized in that the magnetic field generator means comprise at least one magnet ( 13 ) of annular shape arranged around the hollow cylindrical electrode ( 2 ) and for which the axis joining its poles is parallel to the axis X-X′ of said electrode ( 2 ). 
     
     
       13. A discharge lamp according to  claim 1 , characterized in that the magnetic field generator means comprise one or more NbFeB magnets. 
     
     
       14. A discharge lamp according to  claim 1 , characterized in that the magnetic generator means comprise one or more magnets ( 13 ) arranged in a metal coupler ( 15 ) and held in said coupler ( 15 ) by electrically insulating parts, said coupler ( 15 ) being connected firstly to the second electrode ( 4 ) and secondly to the electric field applicator ( 3 ) in such a manner that the magnetic axis of said magnet(s) ( 13 ) coincide(s) with the axis X-X′. 
     
     
       15. A discharge lamp according to  claim 1 , characterized in that the magnetic field generator means comprise an electromagnetic coil of axis parallel to the axis X-X′. 
     
     
       16. A discharge lamp according to  claim 1 , characterized in that it includes cooling means suitable for cooling the magnetic field generator means. 
     
     
       17. A discharge lamp according to  claim 1 , characterized in that the magnetic field generator means present dimensions extending transversely relative to the axis X-X′ that are greater than the projected inside area of the hollow cylindrical electrode ( 2 ) so as to generate a magnetic field that is uniform in intensity and in orientation over the area of the sample ( 12 ) facing the end of said electrode ( 2 ). 
     
     
       18. A discharge lamp according to  claim 1 , characterized in that it includes means for measuring the intensity of the magnetic field and suitable for comparing the intensity of the magnetic field at the sample ( 12 ) with a predetermined threshold. 
     
     
       19. A method of improving a glow discharge spectrometer discharge lamp ( 1 ), the method comprising the steps of:
 applying a continuous, pulsed, RF, or hybrid electric field to the terminals of the electrodes ( 2 ,  4 ) of a discharge lamp according to  claim 1 , and suitable for generating a plasma for ablating the surface of a sample ( 12 ); and 
 
       characterized in that it includes the step of:
 simultaneously applying an axial magnetic field of field lines parallel to the axis X-X′ of the hollow cylindrical electrode ( 2 ) of said discharge lamp, said magnetic field being uniform in orientation and in intensity over an area of the sample ( 12 ) that is not less than the inside area of the cylindrical electrode ( 2 ) as projected along the direction X-X′.